When research began in 1977 on A Golden Thread: 2,500 Years of Solar Architecture and Technology, the sire of my new book Let It Shine, only 360 watts of photovoltaics operated in the world. At this writing, that installed number has increased by a factor of 250,000 to 100 billion watts, or 100 gigawatts. Likewise, when I wrote From Space to Earth: The Story of Solar Electricity 14 years ago, the largest photovoltaic panel factory had a capacity to build 10 megawatts of product per year. Currently, a typical factory will have the ability to manufacture hundreds of megawatts. The world’s solar water-heating market, too, has grown more than twentyfold over the past 13 years.
Few realize the value of solar energy today. Even fewer know its lineage.
Many believe that solar energy is a late-20th-century phenomenon, yet 6,000 years ago the Stone Age Chinese built their homes so that every one of them made maximum use of the sun’s energy in winter. Twenty-five hundred years ago the sun heated every house in most Greek cities.
“For well-being and health, the homestead should be airy in summer and sunny in winter. A homestead possessing these qualities would be longer than it is deep; and its main front would face south.”
No one today thinks of Socrates as a solar-energy promoter, for example. Yet never in history has there been a stronger or more eloquent advocate for the use of solar building principles. Xenophon, a disciple of Socrates, presented in a Socratic dialogue the philosopher’s belief that the art of “building houses as they ought to be” was firmly based on the principle “that the same house must be both beautiful and useful.” Socrates began his discourse by asking a question: “When someone wishes to build the proper house, must he make it as pleasant to live in and as useful as it can be?” After his student answered in the affirmative, the master then asked, “Is it not pleasant to have the house cool in summer and warm in winter?” And when the student assented to this as well, Socrates then closed the discussion by affirming, “Now in houses with a southern orientation, the sun’s rays penetrate into the porticoes [covered porches,] but in summer the path of the sun is right over our heads and above the roof, so we have shade…. To put it succinctly, the house in which the owner can find a pleasant retreat in all seasons … is at once the most useful and the most beautiful.”
The second great sage of Greece, Aristotle, provided additional details not mentioned by Socrates. He, too, started with a question: “What type of housing are we to build for slaves and freemen, for women and men, for foreigners and citizens?” And then he answered, “For well-being and health, the homestead should be airy in summer and sunny in winter. A homestead possessing these qualities would be longer than it is deep; and its main front would face south.”
Socrates’ father worked in the construction industry as a stonemason, and many believe Socrates followed in his father’s footsteps. If he did, he would have known about the remodeling of two houses in downtown Athens—the Agora—where workmen changed the arrangement of rooms so the most important ones would face onto a southern courtyard. The fact that Socrates spent the majority of his life in the neighborhood assures that he knew about the solar project in Athens. And less than two miles outside of the city, another example of solar design was built in Socrates’ time. This was a large rectangular house that sat on the foot of the northerly slope of Mount Aegaleo, one of several mountains near Athens. According to the archaeologists who excavated it, the farmhouse they discovered, “which faces south and has its entrance and court on this side and its main rooms on the north,” corresponds exactly to the ideas expounded by the great philosopher as recorded by Xenophon.
Years later Roman architects published self-help books about using solar energy to show people how to save on fuel as firewood became scarce and as fleets scoured the known world for much-needed supplies of wood.
During the Renaissance Galileo and his contemporaries planned the construction of solar-focusing mirrors to serve as the ultimate weapon to burn enemy fleets and towns. Leonardo entertained more peaceful applications. He aimed at making his fortune by building mirrors a mile in diameter to heat water for the woolen industry.
In the Industrial Revolution, engineers devised sun-powered steam engines to save Europe from paralysis should it run out of fossil fuels. Gustav Vorherr in the 1820s opened the first school of solar architecture, in Munich, and his mentor, Dr. Bernhard Christoph Faust, was the first person to write a complete book on using solar energy. Thousands of architects—trained in the work of Faust and educated by Vorherr—fanned out to build solar-oriented homes throughout Europe in the 19th century.
In 1767 a Swiss polymath modeled global warming by trapping solar heat in a glass-covered box in the same way that carbon dioxide traps solar heat above the Earth. Using the same type of glass-covered box to harvest solar energy, enterprising businessmen established a thriving solar water-heater industry in California beginning in the 1890s. And as electricity began to power cities, the first photovoltaic array was installed on a New York City rooftop in 1884.
As the technology has evolved, solar covers millions of rooftops from China to Greece, and from Germany to jungles of Peru to homes in California.
From the book Let It Shine. Copyright © 2013 by John Perlin. Reprinted with permission from New World Library.